The Prime Minister and the Labour leader have traded blows over the controversial plans for new grammar schools in a series of angry exchanges in the Commons.
Jeremy Corbyn fired the first salvo by asking the Prime Minister about the plans and cited Kent as an area where there was evidence of the shortcomings of selection.
He said GCSE results for Kent showed the system was not working.
"The evidence of selection is this: in Kent 27% of children on free school meals get five or more GCSEs compared with 45% in London. Why does the PM want to expand a system that only lets children down?"
Theresa May said Mr Corbyn should "stop casting his mind back to the 1950s" and that the plans would help the one and a quarter of a million pupils in poor or failing schools.
"When we look at grammar schools and the level of attainment of disadvantaged pupils, the gap is virtually zero. It's an opportunity for young people to go where their talents will take them."
She added: "We believe in equality of opportunity - he believes in levelling down, we believe in levelling up."
But Mr Corbyn went on the offensive, asking whether the existing grammar schools in Kent would have to meet the new conditions on quotas for less well-off children.
"Equality of opportunity is not about segregating children at the age of eleven."
The PM taunted the Labour leader reminding him that he went to a grammar, as had she. "We want to make sure grammar schools are doing the job that we want them to which is providing a range of opportunities. It is Labour that have stifled opportunity."
But Mr Corbyn said: "We should never have a system that divides children at the age of 11. It is not about pulling up a ladder but providing a ladder for everyone."